1. Field of the Invention
This invention relates in general to weaving processes and apparatus and in particular to a stepwise scanning of patterns according to a scanning raster.
2. Description of the Prior Art
Textile fabric patterns are expressed by the variations in the color of the fabric determined by the color pattern or zone and by the texture resulting from the cross-weaving of the fabric as, for example, the manner of joining and looping of the warp and weft threads of the pattern. Initially, an artist prepares a drawing illustrating the color and texture of the fabric which it is desired to be produced. The inking of the colors does not occur until the weaving process wherein the corresponding yarns are selected, but the texture of the weave must be taken into consideration during the preparation of the control data. The pattern which is designed exclusively according to the artistic aspects, is therefore converted into a weavable pattern from which the weaving technique structure of a fabric can be accomplished. For this purpose, in a second process, a technical fabric textile drawing also called a point paper design is prepared from the pattern design. The drawing is reproduced on pattern paper printed with an orthogonal raster network. The space between two horizontal raster lines is called the weft line and between two vertical raster lines the warp line. In the subsequent fabric at least one weft thread runs in the weft line and at least one warp thread in the warp line. Each raster stitch (loop, mesh) of the pattern element represents a crossing point between the warp and weft threads. The interval of the raster lines from one another corresponds to the warp/weft ratio which is a criteria of the fineness of the fabric.
In practice, the entire pattern design is generally not converted into a point paper design but rather only a pattern repeat wherein the term "pattern repeat" is to be defined as the smallest regularly recurring pattern detail.
The transfer of a pattern repeat occurs by means of filling out or leaving free pattern elements and whereby curved lines of the pattern design are approximately weaved by step-shaped contours. There are two different embodiment forms of the point pattern design with one embodiment comprising a fully drawn out completed point paper design in which all thread crossing of the warp and weft are exactly entered in the raster network. A pattern element which is blacked in means, for example, a warp raising; and blank pattern elements represent a warp lowering. During the scanning of such point pattern design, therefore, only a black-white decision must be made.
The second embodiment comprises a point paper design produced without ties in which the point paper design pattern elements associated with a fabric zone with the same tying effect are characterized by color. This requires the indication of the tying information associated with each pattern color. If various tying effects occur in a fabric pattern the point pattern design contains different colors which must be recognized and evaluated during the scanning of the point pattern design.
In a third pattern step, the color data is obtained with the use of a point pattern design scanning device.
In a known self-acting point pattern design scanning device, the point pattern design prepared from a weaving pattern design is attached to a rotating scanning drum and scanned pattern element by pattern element by a light dot by a scanning instrument means which is movable parallel to the scanning drum. The scanning takes place on circular circumferential lines of the scanning drum which run centrally between two vertical raster lines. After the scanning of a circumferential line, the scanning instrument means is shifted axially for a distance interval between two circumferential lines and subsequently the next circumferential line is scanned.
The light reflected from the point paper design into the scanning instrument means is converted into opto-electrical analog signals which are fed to a color recognition circuit. The color recognition circuit converts the color information read from each pattern element into a color signal which is transformed by digitalizing into color data for each pattern element. The color data is then stored in a digital storage device.
In a fully completed point pattern design the stored data constitutes the control data for the weaving process. If conversely, a point pattern design which was drawn without the ties being indicated were scanned, the control data for the weaving process will be formed from the scanned color data and the separately stored tying information. The control data is transferred to data carriers in the form of punch tapes, jacquard cards, film strips or magnetic tapes or magnetic discs which ultimately control the work cycle of the weaving machine.
In order to achieve a high recognition accuracy of the point pattern design, color of a design element during scanning of a point pattern design with the aid of an automatically scanning point pattern design scanning device, the contours of each pattern element must be very exactly filled in with color so that the scanning optics can derive unequivocal information at the particular scanning point. The point pattern design drawing must therefore be executed with extreme accuracy and care. This process is very expensive and time consuming and accurate reproductions cannot be made by the weaving machines if the design elements vary by as much as 1 millimeter in very fine textile patterns.
The accuracy in the recognition of a color can also be increased in the case of an inexactly drawn point paper design if the information in each case read by the scanning instrument means is that information at the center of a pattern element. At such center point, the color inking is surely present.
In an automatically functioning point paper design scanning mechanism in which the scanning mechanism as described executes equidistant advancing steps, a central scanning of the pattern elements can, however, only be achieved if the raster network imprinted on the drafting paper is exactly and precisely executed and the point paper design pattern is accurate in size.
These requirements do not exist in practice. The imprinted raster network is often imprecise and conventional drafting paper is not distortion free. Where the work is not carried out in air-conditioned rooms, temperature fluctuations and humidity changes lead to an undesired length alteration in the point pattern design pattern which can be up to 10 millimeters in the case of an ordinary repeat length of one meter. If, however, as already mentioned the edge length of a pattern design element amounts to about 1 millimeter, it is seen without difficulty that a central scanning of each pattern will not be guaranteed. An additional consideration is that the drafting paper is distorted by varying moisture distribution because of an uneven application of the drafting color inks in the point position design production.
Furthermore, thicker marking lines are often additively inserted into the raster network with results that there are no equidistant points of intersection present or a raster network is completely lacking. The above difficulties can be partially avoided by the use of expensive but more true to size plastic foil for use as the drawing carrier for the point pattern design so that it is possible to operate with a constant step width of the scanning instrument device. Such plastic foil, however, provides a poor adhesion base for the drafting colored ink and a uniform color application can only be achieved with difficulty. The requisite time for preparing the drawing on a plastic foil is thus considerably higher than that required with normal drafting paper. In order to keep the drafting time short and to be able to operate economically, it is desired to continue the present practice of using cheaper drafting paper and to avoid the disadvantages of said cheaper drafting paper by suitable means.
Prior art devices are known which attempt to compensate for the disadvantages of using conventional drafting paper.
In West German Patent OS No. 2,154,878 a device is described in which an auxiliary scanning instrument is utilized beside the main scanning instrument which reads the information on the point paper design. The auxiliary scanning instrument scans a scale arranged outside the point pattern design whose division in each case is located centrally of two vertical raster lines of the point pattern design. With a corresponding alignment of both scanning instruments the auxiliary scanning instrument always generates a control pulse when the main scanning instrument is located in the center of a pattern element. At this time, the control pulse causes the main scanning instrument to derive a sample from the point pattern design.
It is further proposed to scan the vertical raster lines of the point paper design pattern itself with the auxiliary scanning instrument. This method presupposes that a raster network is present and that the available raster network is very well constructed so that recognition is possible.
Another device is described in German Patent OS No. 2,204,710 which contains an auxiliary scanning instrument for producing a control pulse by scanning vertical raster lines. In order to avoid the emission of a control pulse when the raster lines are insufficiently expressed, a pulse generator is additionally provided which is synchronized with the control pulses in such a way that it generates auxiliary pulses at the same rhythm as the control pulses. When a control pulse is absent because a raster line is not identified, the auxiliary pulse establishes the point in time of the scanning.
German Patent OS No. 2,023,607 discloses a process in which a longitudinal strip of the point pattern design is provided with a raster network which is maintained free of ink registrations and is separated from the pattern just before the scanning and clamped into an auxiliary device. This longitudinal strip is then also scanned by an auxiliary scanning instrument so as to obtain control pulses.
Instead of printed raster lines magnetic lines can also be applied to the point pattern design and can be scanned with a corresponding scanning device.
In the above mentioned processes, a raster network is a prerequisite where all raster lines or at least the majority of the raster lines are strongly expressed. Raster lines which are barely visible have to be retraced by hand. The main and auxiliary scanning instruments must be precisely aligned.
In German Patent OS No. 2,424,457 a scanning process is described in which the scanning instrument is automatically shifted in the warp direction independent of printed raster lines and of possible dimensional fluctuations in the point paper pattern. In the scanning device described therein, the point pattern design is attached to the scanning drum in such a way that the weft line runs in the circumferential direction and the warp lines in the scanning direction. During scanning, the scanning drum rotates continuously and the scanning instrument carries out a stepwise axial advancing movement by means of a stepping motor wherein each case after the scanning of a weft line a partial shifting to the next line occurs. For determining the magnitude for partial shifting, the integral quotient is formed before scanning from the number of motor pulses which occur during the length of the point pattern design in the warp direction and from the number of stitches in the step direction. The integral quotient is the specified nominal quantity for the control of the stepping motor.
The motor pulses actually emitted during the advancing movement of the scanning instrument are counted as the actual magnitude and compared to the nominal magnitude and when these are equal the partial adjustment and the counting cycle are ended by resetting the counters.
The above explanations relate to prior art means for obtaining data for operating weaving machines. Similar problems also exist in the generation of control data for other textile processing machines.